Research And Design Of Fractional Frequency Synthesizer In 24GHz FMCW Radar Transceiver

Currently, automotive radar is playing a very important role in the automotive safety driving, and frequency synthesizer is an indispensable part of radar transceiver frontend system. Its performance often determines some key parameters of the entire radar system.In order to meet the requirements of radar transceiver, the performance of frequency synthesizer should be optimized from the loop parameters and module circuits design. The main achievements of research are as follows.Firstly, the loop parameter and phase noise of frequency synthesizer are analyzed, and the requirements of frequency synthesizer applied in radar transceiver are given.Secondly, the RF module, analog module and digital module are respectively analyzed. In order to implement lower out-band phase noise and lower power,24GHz low phase noise VCO and low power prescaler are realized. In order to design a low current variation and low current mismatch charge pump, a current compensation technique is applied. In order to meet the requirements of frequency synthesizer, the Mash 1-1-1 sigma-delta modulator and waveform generator are discussed.Thirdly, the RF module including VCO and two-stage divider are implemented in the TSMC 65nm CMOS process. The chip area is 0.8mm*0.62mm and the power consumption of whole chip is 35mW. When the output signal frequency of the last divider is 5.89GHz, the measured phase noise at 1MHz offset is -111dBc/Hz.Finally, loop parameters of fractional frequency synthesizer are analyzed and designed. The circuit design and layout design of the whole system are implemented in the TSMC 65nm CMOS process. The simulation results show that the locking time is 3us. The layout area is 1.5mm*0.87mm (including PADs and IO circuits).